To respond to issues of an economic and ecological nature, airlines are seeking to decrease aircraft fuel consumption. With this aim, they are asking constructors to provide technological solutions making it possible to design aircraft that consume less fuel but are also asking them about solutions for operating their air fleet that make it possible to reduce fuel consumption. With this objective, several taxiing procedures exist which are intended to reduce fuel consumption.
A first procedure consists for example in taxiing under certain conditions with a smaller number of engines than the number of engines of the aircraft, for example on a single engine for an aircraft with two engines or on two engines for an aircraft with four engines. For example, for a twelve-minute airport taxiing procedure, the saving in fuel is about 40 Kg for a short- or medium-haul twin-jet and 100 Kg for a long-haul twin-jet. For a company operating a sizable fleet of aeroplanes, the operating costs can be significantly reduced, especially within the context of the high petroleum price.
However, limitations exist for reasons of lifetime of the propulsion means and of procedure of use before a takeoff phase and of use after the landing phase. The taxiing procedure based on a reduced number of propulsion means is also not recommended for a heavy weight. It can also give rise to accelerated wear of the brakes, be prohibited on certain airports due to the damage caused by the blast of the engine which is stronger. Moreover for redundancy reasons, the taxiing procedure must be applied with the Auxiliary Power Unit (APU).
A second procedure consists in taxiing by means of a towing vehicle. The propulsion means must however be started up or shut down according to a particular procedure dependent particularly on minimum operating time before and after takeoff and landing.
A third procedure also exists, conceivable for the future, consisting in taxiing by means of an external electric motor positioned on the aircraft. For the same reasons as the previous procedure, the pilot must comply with a specific taxiing procedure dependent on the conditions of use of the onboard propulsion means and must in the case of this procedure also take into account the conditions of use of the electric motor.
Consequently, the application of the various taxiing procedures requires the checking of several implementation conditions.